A study has found microbes on dollars which include DNA from our pets, traces of drugs, and bacteria and viruses that cause disease. The findings demonstrate how money can silently record human activities, leaving behind so-called "molecular echoes.

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A study has found microbes on dollars which include DNA from our pets, traces of drugs, and bacteria and viruses that cause disease. The findings demonstrate how money can silently record human activities, leaving behind so-called "molecular echoes.